The invention relates generally to power-driven conveyors and, more particularly, to conveyors with roller belts having rotatable article-supporting rollers that roll on a bearing surface at the infeed end of the conveyor as the belt advances.
Roller belts are used in material-handling conveyors to increase the separation of conveyed articles by accelerating the articles along the conveying surface at a speed greater than the speed of the belt itself. Roller belts are typically characterized by a plurality of freely rotatable embedded rollers whose diameters exceed the thickness of the belt. In this way, salient portions of the rollers extend past the top and bottom surfaces of the belt, as shown in FIG. 7. The rollers 10 of the belt 12 ride on a bearing surface 14 under the carryway portion of the belt's path. As the belt advances in a direction of belt travel 16, the rollers are rotated in the direction of arrows 18 by their contact with the stationary bearing surface. The rotation of the rollers propels articles atop the rollers in the direction of belt travel, but at a higher speed—typically twice the belt speed if the rollers do not slip on the bearing surface. Because of the conventional positioning of idle sprockets 20 at the infeed end of the roller-belt conveyor, the bearing surface, to avoid interference, extends upstream to a position 22 downstream of the sprockets, which engage the belt between rollers. Until the rollers making their way around the sprockets reach the bearing surface, they do not rotate. Because the rollers 10′ immediately at the infeed end of the roller-belt conveyor are not rotating, there is a delay before articles transferred onto the conveyor are accelerated on the belt and separated from trailing articles.